feat(utils): add sine spacing

+af_tools/+utils/spacedvector.m

 function vect = spacedvector(spacing, nPoints)
     % SPACEDVECTOR Returns a vector based on chosen spacing and number of points
     % -----
-    % (c) Copyright 2022 University of Liege
+    % (c) Copyright 2022-2023 University of Liege
     % Author: Thomas Lambert <t.lambert@uliege.be>
     % ULiege - Aeroelasticity and Experimental Aerodynamics
     % Apache 2.0 License
@@ -18,6 +18,9 @@ function vect = spacedvector(spacing, nPoints)
         case 'cosine'
             beta = linspace(0, pi / 2, nPoints);
             vect = 1 - cos(beta);
+        case 'sine'
+            beta = linspace(0, pi / 2, nPoints);
+            vect = sin(beta);
     end
 
 end